To those of you towing with gauges,how are your ECT vs. EOT differentials looking while towing? For instance if you tow on a flat road at highway speeds what are your temp. differentials? I know you will have temp. spikes while cresting hills and all that but I'm wondering about STABILIZED temps. on a flat rd..I know about the 15 deg. rule of thumb but does this apply while towing also or is it the rule of thumb with no load? I have an average of 9 deg. diff. running empty so I think I'm OK but I'm gonna tow my tractor tomorrow (approx. 9,000 lbs.) on a fairly flat rd. around 65 mph. and just wanted to have other peoples temps. to compare mine with.Thanks in advance for the help!!

 

15 degree rule applies empty or loaded once temps have stabilized on level ground at highway speeds.

 

Thanks Cj,I wasn't sure about that.Do you see a big diff. in your temp. spreads towing vs. empty? I know your temps. are gonna rise some,but will the differential become greater or do they usually both go up together and the differential remain approx. the same? Not trying to be a PIA,just trying to learn something!!

 

When I tow in the mountains on a hot summer day, I'll maintain the 15 degree spread on the steep climbs, but both temps get hot. The oil temp runs ahead of the coolant temp because the oil is being sprayed internally at all the hot spots. In reverse, when coasting down the hill, the coolant will cool faster than oil, but in both cases, the 15 spread is maintained. I'll tow some pretty steep passes in hot weather, and the only time I've had to back off is when the EGT starts getting over 1250, I set that as my limit. On a hot day with a steep climb, the EGT and the eot get pretty hot, and when that fan starts roaring, you know she's working up a sweat. Never had to back off more than a mph or two on the cruise control to get the temps cooler. This is where a good set of gauges is really important. With a ect eot and egt, you get all the important info you need to take care of the engine when towing. Just heading up a steep pass with a heavy load on a hot day without gauges is like playing russian roulette, because you certainly can put the engine in a bad place if you just put your foot in it and go. She'll do that a time or two, but then you get into the pay me now or pay me later scenario.

 

Thanks for the help! It sounds like you can realistically stay inside the 15 deg. diff. while working it pretty hard. That's what I needed to know. I'm gonna tow tomorrow and monitor my temps. but I'm a flatlander.LOL!! No hills around here.

 

For me, the ECT in the mountains lead the EOT's going up and is also the quickest to cool down. As oil is thicker than water (coolant), this sounds reasonable to me! Just a month after a EGR/oil cooler replacement both temps stayed within 15 * of each other even when going up/coming down!

 

What are you using to monitor these temps? Are they actual gauges and if so where did you put the sending units for temp sensing.

 

I use Scangauge II for my gauges. Through the OBD port from the PCM.

It does not read EGT, Fuel Pressure, Oil Pressure.
$160

Some use Edge Insight. around $285, if you get it with EGT probe, $350 or so.

 

Just pulled my trailer (about 9000lbs) 2300 miles from nh to tn on route 81 through virgina some pretty good grades.
ECT 190 to 200
EOT 196 to 218
TFT 154 to 170
EGT 550 to 900
On acouple of the long grades hit 20 degree diff but dropped very quick once over them.
My cooler was replaced about 20,000 miles ago

 

I use the Edge insight w EGT couple. (the old one not the CT)

 

Thanks, I have all autometer gauges and I think some of my coolant temperature concerns now could be sensor location. I am reading coolant temp down on drivers side block.

 

I pulled my tractor this morning (approx. 9,000 lbs.) and I was pretty happy with my results.It was approx. 60 deg. this morning. I had a 10 deg. temp. spread (on average) running 60 mph. (55 mi. speed limit,don't need a ticket),turning approx. 1,800 RPM. The ECT stayed around 196,the EOT stayed around 206.The terrain consisted of SLIGHTLY rolling hills,(about as flat as you can find) not enough hill to make the truck downshift. My temp. spread seemed to close up on the slight uphill grades (approx. 8 deg. spread) and the spread would open on the downhills (10-11 deg. spread). The slight uphills were just enough to pull about 10 psi. boost and the downhills (obviously) no boost. I have to say,this does make me feel better because I had an average 9 deg. diff. empty so I thought maybe I had a potential problem but I guess the load (on flat ground) doesn't make much difference to the spread.I'll hit the interstate after work and see what happens at 70 mph. in the heat of the day (it's supposed to be 83 deg. today) but I don't expect to see much difference.Thanks for all the help,it is appreciated!!

 

4 to 6 deg. diff. while easy cruising
7 to 8 deg. diff. while driving like i stole it.
11 deg diff while towing a 12k 5th wheel.

 

On the way home yesterday with the tractor in tow (9,000 lbs.)I took the interstate. I ran 65 mph. (traffic wouldn't let me maintain 70)with approx. 83 deg. ambient temp. Surprisingly(to me),my temp. spreads were LESS at 65 mph. than at 60 or even 55 mph. I was getting a 10 deg. spread at 60 mph.,and an 8 deg. spread at 65.It appears that a moderate engine load helps build ECT up a little,while the EOT still remains fairly constant. My theory is running 65 mph. was enough to get the engine "working" a little CONSTANTLY (thus building more heat inside the engine) and bringing the ECT up a little and opening the thermostat to full flow vs. slower speeds not building enough heat to FULLY open the thermostat CONSTANTLY to allow full coolant flow. After I got off the interstate and got back on the 2 lane my temps. were approx. 11 deg. diff. at 55 mph. Maybe I'm nuts,but my theory sounds reasonable to me. All this tells me that we need to be careful jumping to the conclusion that our oil cooler is clogged if we are seeing close to 15 deg. temp. spreads without working the engine a little. Does my theory sound reasonable to ya'll or am I a nut?

 

Yo'll have to draw your own conclusion on the nut item, however my spread varies 4 to 10 degrees wether loaded or not depending on the terrain and ambient. Mostly terrain.